Acoustic switch



Oct. l, 1935. E. PRAETORIUS ET A1.

ACOUSTIC SWITCH Filed Aug. 7, 193,1

(Zalig. 4

as sound Waves. v.

vention, however, can be utilized to perform-a VPatented Oct. l, 1935 UNITED" V*s'I-Afnazs PATENT OFFICE ACOUSTIC swrrcn Edward ,Praetorius and Nathan E. Joaquin, Los Angeles, Calif., assigner-s of one-third to John E. Stewart, Los Angeles, Calif. i

This invention relates to a circuit controlling device, and more particularly to a device that controls a circuit in response tothe reception of minute elastic impulses of high frequency, such In its broader aspect the incircuit control function in response to mechanical vibrations. A

For example, the device can be placed inthe path of sound waves, such as those emanating from an automobile horn, in order to initiate the operation of a traffic signal, or the opening or closing of a. garage door. It is accordingly one of the objects `oi. this invention to provide a switch that responds to very Weak mechanical vibrations, such as those received from a horn placed even as much as a hundred feet or more from the device.

1n receiving such vibrations, and in converting the energy thus received intoone capable of opening or closing a circuit for an operable period, certain problems are met with which will now be discussed. Sound vibrations, for example, have a range of from about ten per second to as high as many thousands per second. If a diaphragm is placed in the path of these vibrations, this diaphragm will vibrate at the frequency received by it; but the mechanical movement is very slight and the frequency of vibration is so rapid that a contact operated thereby cannot perform a control function in ordinary circuits during any vparticular vibration.

It is true that by appropriate amplifiers these vibrations can be faithfully reproduced as variations in current flow; but no relay,'operating a switch, can respond fast enough to control the switch. With the aid of our invention, these extremely rapid vibrations are translated into very much slower vibrations that are capable of operating such relays when the relays are properly designed. In general, the period of opening or closing of the contacts that operate the relay can be lengthened by the aid of this invention, to a very large multiple of the period of each vibration received.

We accomplish these results by providing a pair of contacts that are operated by the kinetic energy of atrain of waves. We 'believel that our device integrates the very small energy increments of a number of succeeding vibrations, but we do not Wish to restrict the scope of the invention to any theory.

Our invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of our invention. YFor this purpose we have shown a form in the drawing accompanying and forming part of the present specification. We shall now proceed to describe this form in detail, which illustrates the general l5` y principles of our invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of our invention is best defined by the appended claims.

Referring to the drawing: 10

Figure 1 is a front, elevation of a device embodying our invention;

Fig. 2 is an enlarged sectional view taken along plane 2-2 of Fig. 1;

Fig. 3 is a further enlarged detail section, taken 15 along plane 3 3 of Fig. 2; and

Fig. 4 is a diagrammatic view, partly in section, illustrating the manner of mounting the device. f i

First of all, the` elastic waves propagated 20 through the air or from anyother medium is translated into mechanical motiomas by the aid of a thin diaphragm I I. This diaphragm is made from stiff material such as' mica, and can have a thickness oi about nine thousandths (.009) of an 25 inch. In order that it be sensitive to weak vibrations,'its exposed area can be made quite large Ain diameter; for example, about 8 inches.

This diaphragm is clamped at'its edge between two yielding rings I2, I3, each about one-sixteenth 30 of an inch thick and made for example from cork.vv The clamping is accomplished by a pair of rings I4, I5. One of these rings,` such as Il, can be provided with an annular recess to accommodate the rings I2, I3 and the diaphragm II. 35 In order to mount the diaphragm I I and its supporting structure in such a manner that extraneous mechanical vibrations shall not affect it, there are provided a pair of resilient supporting projections I6, I1 on diametrically opposite 40 sides of the ring I4. 'I'hese projections can be conical and can be made from soft rubber or the like and can be held in place asl by screws I8. They can be pinched, as indicated at I9, in apertures in side walls 20 of a supporting box such 45 as 2I (Fig. 4). 'I'he projections thus permit the diaphragm structure to be angularly adjusted about the axis of these projections. Such angular adjustments may be desirable as explained hereinafter, to makethe plane of diaphragm II 50 assume an oblique position for causing gravity to act on the control contacts in lieu of a weak spring or the like. f

- 'I'he box 2| can be made from sheet metal with v a removable or hinged cover 22 at the back; and 55 at the front, an opening 23 can be provided to permit the passage of sound waves into the box 'when these sound waves are properly directed.

A supplemental support 24 for the lower edge of the structure can be placed inside the box, and can be provided with a layer 25 of rubber or the like.

One of the cooperating contacts operated by the vibration of diaphragm Il can be supported at or near the center thereof. It can take the form of a threaded post 26 passing through the diaphragm, having a knife edge insert 21 at one end. This insert can be made from a noble metal to provide good conducting properties, as, for instance, of chemically pure silver, or gold or platinum. The post 26 can be held in place in the center of the diaphragm Ii by the aid of nuts 23 engaging opposite sides of the diaphragm and threaded on the post. In order to stinen the diaphragm Il slightly at its center, washers 23 of thin mica can be placed on opposite sides thereof.

, Contact is normally made between the member 21 and a mobile velectrode or contact 3U. This is in the form of a ball of about one-eighth (V.) of an inch in diameter and also made from a. noble metal. This ball is urged against the contact 21 as by gravity, Its movement is restrained or guided in a square channel member 3| also made from noble metal. As shown most clearly in Fig. 3, the contact 21 is in a diagonal position with respect to the member or guide 3|. Furthermore, this guide and the contact 21 are of such proportion with respect to mobile contact 30 that they cooperate to form a'three-point support for the ball when the diaphragm is in the inclined position of Fig. 4.

'I'he guide member 3| is soldered or otherwise supported in a sleeve 32 threaded into a supportlng arm 33. This arm is supported on ring I5 as clearly shown in Figs. 1 and 2. A depending nange 3l overlies the sleeve 32 to shield it; and a thumb screw 35 is threaded into the outer portion of the threaded aperture in arm 33 for confining the ball 30 in the space dened by guide 3| 'Ihe operation of the device is such that the kinetic energy of the vibrating diaphragm II acts to separate the ball 3|! intermittently from contact 21 for a substantial period. This separation of the contacts opens a circuit that may control a, relay or the like. We shall now describe in detail just how this operation is effected.

With the diaphragm structure inclined as indicated in Fig. 4, and no vibrations received, it is apparent that the ball 30 is held against knife edge 21 by gravity, and that this ball is confined by the two adjacent walls of the guide 32 which slope upwardly away from the knife edge contact. When vibrations are received, the diaphragm Il vibrates and the' post 26 imparts a rapid kick to the ball 33, sending it up the infclined guide. As it rolls up the incline, the circuit is interrupted and stays interrupted until the ball rolls down the incline. The blow imparted to ball 3l is produced by the kinetic energy of the vibrating diaphragm and of post 26, which is purposely made long enough to supply the proper amount of mass to the moving system. For ensuring that the ball 30 will not roll back too quickly, the inclination of guide 3l from the horizontal is made slight, as by keeping the plane of diaphragm Il not far from the vertical.

The period of separation of the ball 33 from contact 21 can be made very much longer by properly proportioning the arm 33. Apparently there is a definite cooperation between the natural frequency of vibration of this arm and the vibrations of the diaphragm Il. Thus the vibrations imparted to the arm 33 by the energy received by the device serve to act on ball 33 to facilitate its movement away from contact 21 or to retard its return thereto. In one form of switch we have devised, the natural frequency of the arm 33 was of the order of several hundred, 1U and this seemed to produce the desired eil'ect. For example, if arm 33 were made rigid as by providing a still' brace for it, the ball 30 is not kept out of contact with member 21 for as long a' period as otherwise. From observations made on an embodiment, the period of separation of -ba11 3U and contact 21 when the plane of diaphragm Il is sixty-seven degrees from the horizontal is hundreds of times the period of the vibration of diaphragm Il.

When the diaphragm Il is actuated, the ball 30 is thus thrown by kinetic energy up the guide 3| and is periodically returned. Its period of separation from contact 21 is, however, sufllcient to operate a properly designed relay.

The mode of connecting the members 21, 30 into a control circuit can be provided in any appropriate fashion. For example, a lead 38 can be joined to post 26 as well as to an insulated binding post 31 supported in rings Il, I5. A lead 33 can be joined to the post from the circuit to be controlled. Another binding post 33 is grounded to the structure. Thus the other lead 40 from the controlled circuit is placed in metallic connection with the arm 33, sleeve 32, guide 3| and finally to ball 3|). When ball 3|| rests on contact 21, the circuit is completed from ball 3l) to this contact, lead 33, post 31, to lead 33. When the ball is separated from contact 21, thisclrcuit is interrupted thereby.

We claim:

1. In a circuit controller, a member arranged to be directly vibrated by the reception of sound waves through the air, a striker carried thereby, a mobile contact arranged to be struck by the striker, and an inclined guide for the mobile contact. A

2. In a circuit controller, a member arranged to be directly vibrated by the reception of sound waves through the air, a striker carried thereby, a mobile contact arranged to be struck by the striker, and a vibratile guide along which the mobile contact moves.

3. In a circuit controller, a member arranged to be directly vibrated by the reception of sound waves through the air, a striker contact member carried thereby, a ball contact, and an inclined vibrating guide for the ball contact, the incline being upward from the striker contact member.

4. In a circuit controller, a diaphragm arranged to be directly vibrated by the reception of sound waves through the air, a striker member can'ied at the center thereof, an inclined guide leading upwardly from the member, a mobile contact on the guide and urged by gravity toward the striker member, and means for mounting the guide so that it can vibrate when the diaphragm is actuated.

5. In a. circuit controller, a member arranged 7u to be directly vibrated by the reception of sound waves through the air, a striker carried thereby,

a mobile contact arranged to be struck by the striker, and a vibratile guide along which the mobile Contact moves, the natural period of vibration of the guide being of the order of several hundred per second.

6. In a circuit controlier, a diaphragm arranged to be directiy vibrated by the reception of sound waves through the air, clamping rings i'or the diaphragm adjacent the edge thereof, a post sup ported at the center oi.' the diaphragm, a. knife edge .contact member carried by thel post, a vibratile arm supported at one end on one of the clamping rings and extending substantially radially to the center of the diaphragm, a rectanguliar guide member carried by the arm and having an axis perpendicular to the plane o1' the dia- 5 phragm, said knife edge extending to the guide and arranged in diagonal relation thereto, and

a bau Contact supported by the guide and me knife edge.

'1. In a circuit controller, a diaphragm arranged to be directly vibrated by the reception' of sound waves through the air, means for supporting said diaphragm adjacent the edge thereof, a striker contact member carried by said diaphragm, a vibrating arm supported at one end on the supporting means and extending towards the striker contact member, a. guide member supported on the arm over the striker contact member, and a ball contact member supported by the guide member and the striker contact member.

EDWARD PRAE'DORIUS.

NATHAN E. JOAQUIN. 

